Racing exhaust for laker 49 OMC

[Tim Kurcz]

For lakers and river runners: Finally, a bolt-on high performance exhaust system for your 49.9 OMC loop triple. This new design replaces the long runner “sandwich plate” type, and features short, Mod-50 style interconnects to enable high RPM use. Designed for the factory powerhead adapter without modifications. It’s water cooled and will fit underneath the existing cowl. Images are the casting pattern mockup. Finished system will have provision for the starter solenoid

The kit will include all parts, fasteners, and gaskets. Taking orders now for spring 2012 kit. Please PM if interested. Thanks,

Tim

[Fast Fred]

:cool:, i needs one.

[88workcar]

Are the production ones going to made out of treated lumber? I think that in the wet conditions that would be a better choice for the duration.

[rustnrot]

Are the production ones going to made out of treated lumber? I think that in the wet conditions that would be a better choice for the duration.

HA! I doubt it, that chip board is there for a reason. When it gets wet, it expands, that's why they call it an EXPANSION chamber!

[OUTBOARDER]

For lakers and river runners: Finally, a bolt-on high performance exhaust system for your 49.9 OMC loop triple. This new design replaces the long runner “sandwich plate” type, and features short, Mod-50 style interconnects to enable high RPM use. Designed for the factory powerhead adapter without modifications. It’s water cooled and will fit underneath the existing cowl. Images are the casting pattern mockup. Finished system will have provision for the starter solenoid

The kit will include all parts, fasteners, and gaskets. Taking orders now for spring 2012 kit. Please PM if interested. Thanks,

Tim

am interested in adapting bolt on chamber for hydro racing and
adapting under base plate for out the side of 15" mid " smackdown racing "

[Fastjeff57]

What will the insides look like?

Jeff

[marchettih2o]

Agree with Jeff...also, What performance gains have you calculated or better yet, actuals?

Thanks, George

[Fast Fred]

:cool:

[michael]

Will this fit under the cowl and inside the lower pan or would they need to be modified?
Looks similar to what Nydahl created decades ago

[Tim Kurcz]

Thanks for writing. This is the first time I've heard of the Nydahl system you mention - have never seen one to be sure! If anybody has one of these, images, or performance experience please contact me.

The only reason I patterned this was at the request of river racer friends frustrated with the RPM limitations of the factory system. The plan is to make it a bolt-on mod that will fit under the cowl and offer Mod-50 style short interconnects. I've got facrory Mod-50 systems to emulate.

Anyway, if five racers commit on/before Feb 15, the project will be developed in time for spring 2012 deliveries. Estimated kit price is $450 plus shipping.

Thanks to all of you that have PM'd. Please be patient, I'll be in touch with you soon.

Tim

[Tim Kurcz]

What will the insides look like?

Jeff

Here are basics yet to be developed. Exahust will exist at the factory exist at the bottom of the block. The port will not be cut in the divider until the casting is completed.

Tim

[michael]

I have a Nydahl one. Will try to take some pictures in next day or so

[Tim Kurcz]

Thanks for the offer to send pics. Your help is greatly appreciated!

Tim

[David_L6]

...

[Tim Kurcz]

Hi David, Thanks for posting pics of the Nydahl system. There's not much point to continue development of my pattern, except mine eliminates the boss restriction just south of the #1. Perhaps Pete has access to the patterns and can make more.
If not, will you let me pull a mold from yours for improvement? Tim

[David_L6]

I sold the one in the picture to Burt Hoefs.

[Fast Fred]

them molds are long gone, i tryed to get them years ago, fire wood i was told.

[Fast Fred]

AKA ,yamaha triple style :eek::cool:

[89HST]

I think I'm in on this after I see what my tax return says.

[Fastjeff57]

Have I got this right: The exhaust will exit though a hole in the botom of the box (not yet made in the above photo). I assume the usual exhaust path down the leg is also left open?


Thanks,

Jeff

PS: The reason I'm so interested is that I run Merc triple power heads on Mark 55 type lower units. I recently added external reeds and larger carbs to one of them, but I'm concerned that the Mark 55 tower is way too restrictive. Going to a set up like the above would eliminate that.

[michael]

Maybe a bit late, but here are pictures of my Nydahl system

46158

46159

46160

46161

46162

[Fastjeff57]

Thanks!

I see the exhaust re-enters the tower at the bottom of the box. I suppose a hole could instead be made at one end of the box, leading to an external pipe and muffler (like the photo below).

Jeff

[88workcar]

Tim haven't you made a few like that? With the pipe out the top?

[Tim Kurcz]

Tim haven't you made a few like that? With the pipe out the top?

Yes, I've built 40 or so racing systems over the last 15 years, all with sprayed water cooling. About 12 were down outlet, the rest were top outlet. There are another 5 in production now.

A Nydahl is on the way for duplication & improvement. These will be internally cooled for use under cowl, but can be used for racers also. All will duct exhaust under the powerhead.

Tim

[Tim Kurcz]

Maybe a bit late, but here are pictures of my Nydahl system

46158

46159

46160

46161

46162

Thanks for the excellent pics! The main change that will be made is elimination of the internal boss which interrupts pulse transfer. Not sure why Ray didn't do this originally. Perhaps he did for his own!

Tim

[Tim Kurcz]

Thanks!

I see the exhaust re-enters the tower at the bottom of the box. I suppose a hole could instead be made at one end of the box, leading to an external pipe and muffler (like the photo below).

Jeff

Hey Fast Jeff, Is that a 62 CI alky?

Tim

[OUTBOARDER]

Tim haven't you made a few like that? With the pipe out the top?

Out the top is all about the firing order and which cylinder is plugging the outher;)

The nydahl log box is all about adding volume where the cross pulsing is going on so
cylinders arent swaping flames, it lowers temp in box so squeeze wont burn pistons.
This by no means is the only advantage or reason. Nice thing about chamber is squeeze is moved down stream to tail cone so you can sqeeze more without burning up stuff which means you can go with alot more port timing and reap more power.

hope it helps some one out there

[Fastjeff57]

..."Hey Fast Jeff, Is that a 62 CI alky?"

I wish! It's a plain old Merc 49 inch triple (the motor some people love to hate).

Jeff

[rustnrot]

...But I see 4 spark plugs...

[Mark75H]

Yeah, I think thats Unkie's 62. Same boat he ran the Konig on if I recall. Neither lifted the sponsons off the water

[Fastjeff57]

Correct, Sam. Got the photos mixed up.

Jeff

PS: Are you going to the Pottstown AOMC show in February? I plan to be there and would like to meet you at last.

[Mark75H]

Probably not this year unless there is going to be something there I know about in advance.

[Fast Fred]

um, i need the first plate different than shown, best to correct #2 port for maximum Bang.:cool:

[Mark75H]

I think Fred is correct

[Tim Kurcz]

Out the top is all about the firing order and which cylinder is plugging the outher;)

The nydahl log box is all about adding volume where the cross pulsing is going on so
cylinders arent swaping flames, it lowers temp in box so squeeze wont burn pistons.
This by no means is the only advantage or reason. Nice thing about chamber is squeeze is moved down stream to tail cone so you can sqeeze more without burning up stuff which means you can go with alot more port timing and reap more power.

hope it helps some one out there

Actually, the top outlet pulse order benefit was consequential.

Fighting elusive tuning issues with early "down" outlet exhaust systems, I decided to change to "up" outlet as an experiment to dump exhaust into clean air. This change also made engine rigging easy because the "up" pipe did not require a special steering bar.

Initial complaints of burns caused by incidental contact the "up" pipe on restarts, concern about potential contamination by foreign objects, tall & won't fit in the trailer, etc. These issues were quickly forgotten as the top outlet system tuned easily and seemed to run more consistently than the down versions. Note: It's my guess that water vapor ingestion may have caused tuning inconsistencies.

Anyway, Anthony is correct that an expansion chamber can ultimately produce more power, but this power comes at the expense of weight and complexity. Pound for pound, dollar for dollar, and horsepower for horsepower, there is no better OMC triple exhaust available than my top outlet fabricated steel system. Also to my knowledge not a single megaphone has been dropped in the lake.

Seeing as they've won numerous national & regional titles and set a competition record, it's become the standard for the SE/850cc class. Good enough there are a few copies built by capable craftsmen. Indeed, imitation is the sincerest form of flattery!

Tim

[Tim Kurcz]

OK 49.9 racers,

There was enough interest that the project is going forward. The pattern is at the foundry and will be back next week for finer tuning. You'll see an update mid-February.

Tim

[formeone]

haaa tim,,, have to argue with you on your the best exhaust system out there ,, deff prettiest,,,, mine seem to be working pritty good,,,, was 4 mph over the 1 mile record in feh,,, crappy water prevented us raceing,,,,.... just giveiing ya grief,,,,cheyney

[formeone]

on going project this season,,, a bounce pipe that actually works on the 49.9er,,,, iam very very close,,, and it works with multiple port designe..... shall see..

[Tim Kurcz]

Hey Cheney,

Yeah, yeah; I agree the expansion chamber will make more ultimate power, but at the expense of complexity and weight (especially if triple sliders). Simple and light is good. Would love to see a photo of your record engine up close.........

Meanwhile, many thanks to Burt Hoefs for the Nydahl loaner! Note the cleaned up duct (boss moved external). A few more hours work to go. Should be ready to take orders early March.

Tim

[tunnelvision07]

does this plate work good? Its a little different from the others I have seen on here. Can it be bolted to a stock block? I bought this a while back but, I haven't had time to mess with it yet it yet.

46382
46383

[tunnelvision07]

sorry for making the pictures so big.

[Tim Kurcz]

The Nydahl was made to emulate Mod50 exhaust duct cross section and bolt to the factory "stock" block. It will be interesting to compare cross sectional area of the Hustler in your possession with the Nydahl. Please measure the width & depth and post. I will do the same tomorrow (traveling). Thanks for posting.

Question for the forum: Is the Hustler still available?

Tim

[tunnelvision07]

Are thes the measurements you want? My exhaust will bolt to a factory block? I don't think you can get them any more. I tried to find some info by searching the web but I didnt find much. I could be wrong though.

[David Mason]

They are still available the last I knew. Just call Tim Snider. They also make exhaust for other engines. They have been doing this for as long as I can remember. In fact I have a Hustler Racing sticker in my shop from the 70's.

I know of a couple other builders of this Mod 50 copy as well. There are also many home built models floating around too. I have had great sucuess in simply modifying a stock exhaust. It comes real close to the Mod 50 and the only tools I used was a grinder and dremmel. I guess it all depends on what you want to spend and what you want. There are still ways to make a fast engine without a lot of fancy add on's or specialty custom built compoents.

[Tim Kurcz]

Hey Dave,

Why don't you post images of your modified factory exhaust system so we can see exactly what you do? If there's a cheaper way to emulate a Mod-50 exhaust, your tricks would be greatly appreciated.

Tim

[Tim Kurcz]

Are thes the measurements you want? My exhaust will bolt to a factory block? I don't think you can get them any more. I tried to find some info by searching the web but I didnt find much. I could be wrong though.

Thanks for taking time to measure and post. Apologies for the delay, I'll do the same tomorrow.

Tim

[Tim Kurcz]

Here they are...... Larger cross-sectional area than the Hustler.

Tim

[Fast Fred]

the factory went out of there way to use the mod 50 exhaust, it has volume above the exhaust ports, seein more volume, or close to the same amount, as a good thing.:cool:

[tunnelboat]

This guy bought Nydahl parts and is reproducing a lot of stuff Its called ProFast now.. I would bet he has the core boxes for this exhaust .. I have bought some hard to find hardware from him. And it says on his website he has the exclusive rights to the Nydahl parts.. http://www.wintechenginemachine.com/profast.htm

[DuckLn]

Wish you would make one for a yamaha 3 cylinder 25/30.:D

Would sell like hot cakes down here in duck huntin areas where those motors are more important that your drivers license.

[Tim Kurcz]

This guy bought Nydahl parts and is reproducing a lot of stuff Its called ProFast now.. I would bet he has the core boxes for this exhaust .. I have bought some hard to find hardware from him. And it says on his website he has the exclusive rights to the Nydahl parts.. http://www.wintechenginemachine.com/profast.htm

Just got off the phone with Greg at Wintech. They only have steering & hardware patterns - no exhaust systems.

Tim

[Tim Kurcz]

They are still available the last I knew. Just call Tim Snider. They also make exhaust for other engines. They have been doing this for as long as I can remember. In fact I have a Hustler Racing sticker in my shop from the 70's.

I know of a couple other builders of this Mod 50 copy as well. There are also many home built models floating around too. I have had great sucuess in simply modifying a stock exhaust. It comes real close to the Mod 50 and the only tools I used was a grinder and dremmel. I guess it all depends on what you want to spend and what you want. There are still ways to make a fast engine without a lot of fancy add on's or specialty custom built compoents.

For all interested, I found this post from last year.........

Bob Snider03-20-2011, 05:06 PM
We are back. We have exhaust and down Housings for sale. Exhaust all the way from Yamato to Formula E. Down Housing for 4 Cylinder Mercs and Formula E. Contact Tim Snider at 573-552-2953

Tim

[David Mason]

Hey Dave,

Why don't you post images of your modified factory exhaust system so we can see exactly what you do? If there's a cheaper way to emulate a Mod-50 exhaust, your tricks would be greatly appreciated.

Tim

Trailer is in storage, exhaust in in trailer. Besides Tim, I build my own racing parts as much as I can. I would most likely NOT give someone in the business of building engines to wax my *** photos of the very exhaust that I use to win races. To me that is common sense, and self presevation to those of us that still believe in what we do.

To all those that sent P.M. to me for pics, all in due time. I will address individually when I get the stuff out again. In th emeantime, there are a few builders of exhaust for a three holers, some are listed here, some are not. I can give you contact info of those not listed.

[tunnelvision07]

Thanks for taking time to measure and post. Apologies for the delay, I'll do the same tomorrow.

Tim

no problem glad i could help.

[Tim Kurcz]

Trailer is in storage, exhaust in in trailer. Besides Tim, I build my own racing parts as much as I can. I would most likely NOT give someone in the business of building engines to wax my *** photos of the very exhaust that I use to win races. To me that is common sense, and self presevation to those of us that still believe in what we do.

To all those that sent P.M. to me for pics, all in due time. I will address individually when I get the stuff out again. In th emeantime, there are a few builders of exhaust for a three holers, some are listed here, some are not. I can give you contact info of those not listed.


That's too funny Dave! For any interested, I'll gladly post images of Dave's engine. It uses a factory OMC Mod-50 exhaust system exiting under the tower, NOT the Dremmel ground factory sandwich plate system mentioned earlier (that can't be done).

Tim

[David Mason]

That's too funny Dave! For any interested, I'll gladly post images of Dave's engine. It uses a factory OMC Mod-50 exhaust system exiting under the tower, NOT the Dremmel ground factory sandwich plate system mentioned earlier (that can't be done).

Tim

Tim, lets stop with the richard measuring already. My GOOD engine that has been very competitive to your engines has competed with both a factory exhaust carved out, and a Mod 50 Exhaust. The Mod 50 Exhaust is better, yes. If you want to make an exhaust that will compete and you don't have the cash to purchase one, or you just want to run it on a lake for fun, the factory exhaust carved out will do the job nicely. If you want the truth, I will spill the beans. The actual speed difference I have seen on a GPS using both systems is 2 - 3 MPH. Hardly worth a big investment if you are not competing at the top level with you record setting, Mason waxing, morphed front cover, Mod 50 piston, stroked, special head, $1000 dollar for the flywheel alone engines.... I am sure you have a lot of pics of my engines, a lot of people photograph my engines. You included. I can tell you one thing about my engines, they don't haveMod 50 guts, they don't have a expensive machined morphed front cover, special reeds or flysheel, or even special carbs. It even has a Factory STOCK head. All of mine do. Yet you seem so determined to prove a point by belittling what I do with so little. If I spent the cash you have spent on your engines can you imagine where it would be ? I don't even own a milling machine..... and I don't farm out a lot work. Bore jobs, yes. $25.00 per hole is what I am charged for that. I think it went up to $30.00 this year. What would you charge to bore a 3 Cyl block to 20 over for me ? Heck, you would not even quote me a price on a front cover like I asked. I am on the blackball list I guess. From all the privagte messages you sent me telling me how much of a jerk I am, and how poor I am at building engines, you should learn to let it go. The class is already declineing, the only OMC 3 Clys at Nationals last year in Wakefield was yours, and Josh Kimbles. The rest were 44 mercs, which are a legal engine to run in the class in APBA. But we all know where a 44 stands with a good 3 holer. It stands in the rear.

So Tim, I hope you are happy with what the class has become, you pushed for it, and got what you wanted. The rules this year are even more relaxed, just as you wanted. Pretty soon it is going to be the Jim & Tim show.

[Tim Kurcz]

Wow Dave,

LOL!!! I'd sure like to see those PM's of me belittling your work - because you know they don't exist. And please don't be mad about me about taking full advantage of the rules that had been unchanged since 1991. BTW: Jason Hay, Cheney Street, and others have taken similar advantage as well. Aren't you unfairly targeting me? Anyway, while reading Ron's DIY engine thread, I now understand the problem....... Priorities.

Tim

Belt Drive

--------------------------------------------------------------------------------

I have long thought a belt drive would be a great way to go. Much less expensive to repair than gears. And you could do it between heats if you chewed up a belt. Hard to replace a gearbox between heats.

I always wondered if a snowmobile type clutch would create the ultimate belt drive system for an outboard.

Ron - FYI - I have more money in my mud motor rig for waterfowl hunting than I do in my best Super E Hydro. Those things are not cheap. The Black Death surface drive I would like is 12K for just the engine. I have a 35 Kohler Surface drive now, those are around 10K. Maybe a little less depending on what brand you get.
__________________
Dave Mason
Just A Boat Racer

[David Mason]

Tim, if you want i could post them here. I saved every one of them. Even the emails. I wanted the record in case anyone ever asked. You might want to check your sent items if you still have them. Between you and Anthony, I have a full PM section here. I did print them out and give them to a few friends.

But at any rate, why do you care about me anymore ? I am no longer involved in your class. I was simply pointing out one can make their own exhaust out of a factory system and increase some speed. Why are you against it ? Why do I even ask anymore..... good grief. I know why.

I give up Tim, you are the better, more educated, more skillfull, more HP, prettier engine builder than I am. You and Anthony should work out some pipes together. I am sure they would be smoking.

For all the other P.M.s thanks guys. I will get you the information you want as soon as I get the trailer from storage. I am glad to help those that want it. I have even loaned out complete rigs to guys to try, and they have beaten me.

Tim, I suggest you take charge of the class, and become a comissioner in APBA Mod. It will make your goals a lot easier to achieve in a shorter amount of time. I know you and I will never be friends, so we might as well end this now. I have no wish to further communicate with you. I would greatly appreciate it if you did the same.



Wow Dave,

LOL!!! I'd sure like to see those PM's of me belittling your work - because you know they don't exist. And please don't be mad about me about taking full advantage of the rules that had been unchanged since 1991. BTW: Jason Hay, Cheney Street, and others have taken similar advantage as well. Aren't you unfairly targeting me? Anyway, while reading Ron's DIY engine thread, I now understand the problem....... Priorities.

Tim

Belt Drive

--------------------------------------------------------------------------------

I have long thought a belt drive would be a great way to go. Much less expensive to repair than gears. And you could do it between heats if you chewed up a belt. Hard to replace a gearbox between heats.

I always wondered if a snowmobile type clutch would create the ultimate belt drive system for an outboard.

Ron - FYI - I have more money in my mud motor rig for waterfowl hunting than I do in my best Super E Hydro. Those things are not cheap. The Black Death surface drive I would like is 12K for just the engine. I have a 35 Kohler Surface drive now, those are around 10K. Maybe a little less depending on what brand you get.



__________________
Dave Mason
Just A Boat Racer

[Tim Kurcz]

Will you PLEASE post someting productive for the sport?

Tim

[Fast Fred]

the stock exhaust is a through back from cross flow days, it's for trolling, cuzz weekend fishermen buy new motors. :cool: best melted into some thing else:eek: unless trollin is what your lookin to do.:cool:

[Mark75H]

the stock exhaust is a through back from cross flow days, it's for trolling, cuzz weekend fishermen buy new motors. :cool: best melted into some thing else:eek: unless trollin is what your lookin to do.:cool:


..........http://www.boatracingfacts.com/forums/images/icons/icon14.gif http://www.boatracingfacts.com/forums/images/icons/icon14.gif http://www.boatracingfacts.com/forums/images/icons/icon14.gif

[formeone]

CANT WE ALL GET ALOOONG,,,HEHEHE,,,,,, well let me tell ya straight up,,, after retireing and now getting back into the sport and testing everything i can think of from a poor mans perspectuve,,,, only cause you guys mentioned my name,,, ugg ,,hehe,,, i have bin testing every thing i can thionk off.... different versions of my exhaust bigger dia pipe out let smaller and different box area on the motor,,,,, i have 3 motors allll different in porting also,,, the v-rude like a bit of back pressure,,,, and i dont care what exhaust ya run,,, ya need to cut it .. to tune it to your porting,,,,.. ie pulse tuning,,,, and if ya run it out the bottom,, it doesnt pulse tune,,, cause of the fireing order,, proven to me by a x-merc engineer race engine builder,,,, as far as ignition,,, i run v-rude,, no limit power pack,,,, have bin blowing them every 3 races ,, have head engineer on it for me at rapair.... other wise bullet proof,,, and i turn mine over 8k even with the 11 lbs stock flywheel.... i tried similiarities of tims front case that i built,, ie snowmobile/seadoo,,, intake,, was good but lacked torque,,, so shelved,,,, came up with my own version of reeds useing socke cages,,,, way better down low power and mid and the usuall top end,, since reed usually always open for most part at top end... i use small rods,,ie early motors,, wiseco or v-rude pistons.... since me small budget... i dont bother balanceing them,,,, i do hone rods,,,, as far as porting them have worked over the intake and exhaust,,, moveing the center intake a little better,,, on top end that it,,, the key is in the exhaust port,,, wont tell ya what ,,,but for the 75$ that john meyers charges me.... he my man,,,,,,, as for the intake i have tested big 75hp carbs and the normal 65-75 hp carbs ,,, not mutch differance ,, bigger 75 hp carb suck more fuel that it ii actualy set record with the early 55 or may be 60 hp 3 cyl carb,,,,, smaller venturi,,, as for milling the head,,, dont do much there,,, i have heads stock heads milled up to .250,,, to test,,, got to watch your timeing on the motor,,,, i have tried other peoples heads that advertise v-rude parts on here,,,, they waste of money... slower...,,, you need torque in this class,,,,, also some of the props well known prop builders pedling,, no where neer what ya need.... i run 8"-9" dia,,,,3 blades....,,, as far as boost porting/finger ports like the mod 50.... you guys suk,,,, unless ya want to run small d-mod wheels,,,, the extra ports take the torque out of the motor,,,, ni have worked stock intake over a few different ways to no avail as of real kik in the but power or speed,,, i just match to block,,,,, and i miss match them all the time,,,, this is from cheyney,,, straight up[ ,,, i ran 84mph at lawrance in the turns and 93 on straights,,,, my faster set up was 88mph in turn and 95mph straight,,, but wanted to blow over,,, that 1mile course with new certifed speedo,, old school,,,,,,,, i only wrote this cause i think lots of people think it expensive to race class,,, it not,,, i would spend twice that on a merc.... and have,,,, most people dont realise you need a different boat,, to accomadate the v-rude... like yamato was 30 years ago,,,,what REALLY REALLY gets my goat is people charging alot of money for v-rude parts that arent tested,,, and are NOT that mutch of a improvement..... over what they can do with a grinder themselves,,, seems to me..... if ya cant put a 90 mph ride together in v-rude from what ive coughed up here... e- mail me and will answer your questions,,,,, it not hard,,, iii want the class to grow and push the speeds... my next and in works project 2 piper c-mod/102... also working on v-rude runabout, overdrive,,,mmmm,,,cheyney

[Tim Kurcz]

Cheney is right, The OMC loop triple runs very well as designed with a decent exhaust system. Here's the factory "sandwich plate" system. Wall thickness is 3/32". There's little you can do with it except go fishing. Grind much anywhere and you break into water.

One of my best engines (the Pooch) was exhaust ported with no finger ports, stout compression, Boyesen reeds, and my fabricated steel top outlet exhaust. 95.5 GPS every day down the straights. My Kestrel "special" delivers the century mark, but takes alot more work and $$$.

Traveling again through the weekend, so the "laker" exhaust (improved Nydahl copy) is delayed until the week of Feb 25th. More then.

Tim

[OUTBOARDER]

Well a lot of pontificating been going on but reality will knock sometimes.
inboard APBA mod kilo record was set using NLA Inland Jet pipe on Kawasaki Triple.
Not as much power as three pipes but enough to do the job. The Engine Guy that developed the pipe for inland jet is dead now but I did talk twice about the exhaust system.

PS: I never have given away parts to be tested, I know what they will do beforehand, Just do not need a endorsement based on opinion of someone that is getting free stuff. If you want to know to whom this is adrerssed email me I aint scared.

In closing if you aint got patents you aint a designer.

[sabine river killer]

why was this last picture on ebay

[OUTBOARDER]

why was this last picture on ebay

measured the system and can make them for outboards .
Won't use silicon couplings, v-bands hold up .

[formeone]

just some pics of my 3 motors soon to add another copy of the one that did104mph,,,,bounce pipe motor slowly tuneing on,,, seems to have some good potential 88mph so far...

[Tim Kurcz]

Hi all,

Have been building three NBRA legal powerheads to send down south and stir up some controversy, diverting energy from the exhaust program.

But, just compared the OMC Mod-50 exhaust which sticks out 2.660" from the engine block to the modified Nydahl which is another .090" so it will fit under the factory cowlings.

Many thanks Cheney, for posting images of your work. Looks like alot of work & testing.... I hope your hunt proves out.

Tim

[ultrafast30]

Any updates on your exhaust ?

[Tim Kurcz]

The Kurcz-Nydahl exhaust system is on hold for one more week while four powerheads are assembled. The pattern has yet to be sectioned, welded, and massaged for casting. First castings should be available mid-late April.

Tim

[Tim Kurcz]

Here is the completed exhaust system ready for production. The introductory price is $495 which includes the 6061-T6 divider plate & water jacket, 355 casting, gaskets, and fasteners ready for assembly (plus shipping). Orders for the first run will be taken through April 10 and require a $250 deposit. Shipments will be early-mid May. Please PM your contact information to reserve your system. Thanks for your interest.

Tim

[850cc racer]

Hey Tim,

could you please let me know how far the outer cover sits out from the block?

wondering if it would sit under our sst60 style cowls.

Cheers

Rob

[Tim Kurcz]

The system as shown is exactly 3" measured from the exhaust face of your 49.9 block including gaskets and fasteners. This is about .090" deeper than the OMC factory Mod-50exhaust system. It should just fit under the Stinger and SST-60 cowls.

Tim

[TBuck2003]

Based on .090 it will fit for SURE under both. Had a Mod 50 under a standard Stinger cowl and that fit with NO issues... Looks real good Tim !!!!


Todd

[thornl01]

Expected Performance Gains ?

Would this help also ?

Dimensions ?

[Tim Kurcz]

The custom longer tuner shown will add bottom and mid-range to the 49.9. It would be helpful when running a fully immeresed propellers, or in drag race applicaitons where out of the hole performance is desired. Note that top end will be adversely affected.

With high propshaft positions used in hight speed and/or racing applications, there's enough slip to get the boat on plane and into the higher range powerband provided by the short interconnects offerer with the Mod-50 style exhaust system.

Thanks to Thom for clarifying the ability to fit my "laker" exhaust under factory cowlings. Nobody will suspect anything until you top end them........

Tim

[marchettih2o]

As thorn asked above...."what are the performance gains?"???? Have there been any test performed on a selected boat, running stock, then your system....any noted results/???
Any HP dyno test performed? It would seem these would be questions with answers...if favorable, I would be interested in a system...thanks n advance...george in texas

[Tim Kurcz]

As thorn asked above...."what are the performance gains?"???? Have there been any test performed on a selected boat, running stock, then your system....any noted results/???
Any HP dyno test performed? It would seem these would be questions with answers...if favorable, I would be interested in a system...thanks n advance...george in texas

Hey to George, Lawrence, others. I have no dyno testing and don't plan to pull any. The improved Nydahl is a close copy of the OMC Mod-50 exhaust system.

That factory race engines used close interconnects is self evident proof of the advantages - it raises the usable rev range and horsepower. If you look at the Mod-50 system, the Yamaha copies, and any late model triple or V-6 exhaust you'll see closest possible exhaust port interconnects.

These systems will be built on a made to order basis only. Orders received on/before April 10 will be delivered late this spring. If you don't order now you'll need to wait until next winter.

Tim

PS The planned price went from $450 to $495 for the first run due to complex coring that proved necessary at the casting foundry. The price may change after the first run depending in degree of difficulty in machining.

[Powerabout]

always wondered about the open chest...could we make a better bubble back for the crossflow V4 and V6?

[Tim Kurcz]

Be aware the V6 is actually two banks of triples, each with 120 degree firing order spacing. The triple "pulse tuning" phenomenon only works with this configuration (or multiples thereof).

Twins, fours, and early Merc in-line sixes tuned with 180 degree alternate firing pairs do not get the 120 degree tuning advantage. It should be noted that Mercury later rephased inline six cranks to take advantage of twin stacked triple exhaust tuning.

The answer to your question is no. Engines with other than 120 degree firing order cannot take advantage of the the simple "open chest" exhaust design.

Tim

[Powerabout]

Hi Tim
Yes so the V6 could whilst keeping the banks separate?

[Tim Kurcz]

Hi Tim
Yes so the V6 could whilst keeping the banks separate?

Yes, any engine with banks of three: Exhaust systems should be separated.

In it's truest form, each bank of three should have exhaust ports located on the piston thrust side (starboard side for a RH engines as viewed from the top like the Mod50). V6's power is compromised because the banks feed a central exhaust cavity (the tower).

Does anyone care to guess why?

Tim

[Powerabout]

you gave away the answer ( almost)

[Tim Kurcz]

A strong hint......... Looking for the technical reason for the phenomenon. Willl give a few days.

Tim

[Fastjeff57]

Narrowness. If the exhausts BOTH exited to their port side, the motor would be both wider and non-symetric.

Jeff

[Tim Kurcz]

Indeed, centralized exhaust is used to keep the engine slender. But the questions is:

Why does one bank produce less power than the other even though they both have 120 degree spaced pulse tuned exhaust?

Try again,

Tim

[Fastjeff57]

Okay; the crank is spinning in an opposite directions relative to the charge flow into the transfer ports.

Jeff

[Powerabout]

corriolis effect?
should you run the engine backwards in the southern hemiphere?
and maybe the bores shouldnt be round?

[Tim Kurcz]

The Corriolis effect would only apply to engines near the equator, and we all know engines spin backwards down under - LOL - that only means the opposide bank would produce less power. But why?

Tim

[Mark75H]

Be aware the V6 is actually two banks of triples, each with 120 degree firing order spacing. The triple "pulse tuning" phenomenon only works with this configuration (or multiples thereof).

Twins, fours, and early Merc in-line sixes tuned with 180 degree alternate firing pairs do not get the 120 degree tuning advantage. It should be noted that Mercury later rephased inline six cranks to take advantage of twin stacked triple exhaust tuning.

The answer to your question is no. Engines with other than 120 degree firing order cannot take advantage of the the simple "open chest" exhaust design.

Tim

Merc used 3 + 3 exhaust tuning on the inline 6's starting with the first gearshift motors. Generally the firing order was alternating pairs for balance with odd/even exhaust coupling (1, 3 & 5 in one group and 2, 4 & 6 in the other). The disadvantage was length between these 3 cylinder exhaust groups favored power in the 5,000 rpm range rather than the 8,000 rpm range.

Its not that it wasn't there, it just wasn't there for super top end.

On the T-2 and T-2x race motors they welded 2 3cylinder 49ci cranks together to get 3 + 3 exhaust tuning with close spacing, 1, 2, 3 in one group and 4, 5, 6 in the other exhaust group. Again there was a problem with length ... the original T-2 set up put them TOO close for 7,000-8,000 rpm. Like these OMC side exhausts ... the T-2X used an extended exhaust chest to drop the tuning into the 7,000-8,000 rpm range and get almost 20 hp over the T-2.

[Tim Kurcz]

Merc used 3 + 3 exhaust tuning on the inline 6's starting with the first gearshift motors. Generally the firing order was alternating pairs for balance with odd/even exhaust coupling (1, 3 & 5 in one group and 2, 4 & 6 in the other). The disadvantage was length between these 3 cylinder exhaust groups favored power in the 5,000 rpm range rather than the 8,000 rpm range.

Its not that it wasn't there, it just wasn't there for super top end.

On the T-2 and T-2x race motors they welded 2 3cylinder 49ci cranks together to get 3 + 3 exhaust tuning with close spacing, 1, 2, 3 in one group and 4, 5, 6 in the other exhaust group. Again there was a problem with length ... the original T-2 set up put them TOO close for 7,000-8,000 rpm. Like these OMC side exhausts ... the T-2X used an extended exhaust chest to drop the tuning into the 7,000-8,000 rpm range and get almost 20 hp over the T-2.

As Sam points out, Mercury did use 3+3 for inline sixes, a vast improvement over the 2X3 exhaust tuning; in fact they actually patented the concept. It improved power, but was not as effective as late model triples as the cylinders were too widely spaced - every other cylinder was used - inteconnect distance was still too far apart.

Sam's continues his explantion for the T2 series Mercs which correctly indicates that closer interconnects make another huge improvement. So close interconnects are the ticket for power delivery from close spaced triples (and multiples thereof).

The question stands: Why the power difference between right and left exhaust porting as seen in the OMC FR19S -vs- FR31M, or the opposite banks in any late model V6?.

[Powerabout]

piston rock and hence the piston sealing the exhaust port when the port is below the piston top so the exhaust leaks into the crankcase

[Tim Kurcz]

piston rock and hence the piston sealing the exhaust port when the port is below the piston top so the exhaust leaks into the crankcase


Indeed, torque rock causes exhaust pressure from the "open chest" to leak past the piston skirt into the crankcase, polluting the intake charge and reducing power for the port side exhaust bank.

The problem can't be overcome in a V engine unless dual exhaust paths are used (both banks using starboard side exhaust ports). The solution is simple for port side engine lovers: Run the engine backwards and locate opposite throw wheels.........

Way to go Powerabout!

Tim

[Fastjeff57]

Ah, wouldn't that simply transfer the problem to the other bank?

Jeff

[Mark75H]

Not on a triple

[Powerabout]

Its a shame all the late 500cc jap engine tech has been kept out of the public eye so we have never seen the top end of 2 stroke technology.
I heard Honda worked out the bores should be oval anyone know about that one?
( I dont)

[Bill Van Steenwyk]

that competed in bikes some 10-15 years ago, possibly longer. I don't remember now whether is was a four stoke or not, but for some time the four stokes could compete against two strokes with a "spot" on displacement, i.e. the four stroke could be larger displacement wise compared to the two stroke because of a power stroke every revolution versus one every other revolution with a 4 stoke. I don't remember now whether this was the F-1 class of bike racing or the next class down, but the engine was definitely an oval bore of about 500CC or larger displacement.

It competed for several years and then faded away, for some type technical problem.


ADD: Try Googling "Honda GP Bike History" and then use the search function for NS500. Two connecting rods for each piston, 8 valves per cylinder, 155HP @15,000RPM Four Stoke Year 1987. This will give you info on both 2 and 4 stroke bikes that Honda built to compete in GP 500CC which was the ultimate in engine and bike development for all the manufacturers that competed.

Each "piston" in the NS500 was oval in shape and filled what would be two round cylinders put together to make one cylinder oval in shape. A 750CC version was also made.

[Mark75H]

It was a 4 stroke

[Bill Van Steenwyk]

Its a shame all the late 500cc jap engine tech has been kept out of the public eye so we have never seen the top end of 2 stroke technology.
I heard Honda worked out the bores should be oval anyone know about that one?
( I dont)


I think you see it now and have for several years (latest Japanese technology in 2 stokes) with the GRM and VRP PRO engines built in Italy at this time. Carlo Verona built and may be still building cylinders and other component parts for the Japanese for bikes used in F-1 racing.

I would venture to say those engines are probably the pinnacle now in 2 stroke design, as what used to be F-1 Motorcycles is now "Moto-GP" and is all four stokes in the largest classes. I think they still run 2 stokes in 125 and 250, but not sure.

[Powerabout]

the 2 stokes left the Gp bikes at the end of last year due to some lobbying by Honda

[Bill Van Steenwyk]

the 2 stokes left the Gp bikes at the end of last year due to some lobbying by Honda


The 2-strokes actually left the top class of F-1 bikes several years ago (2002), and I would not doubt that Honda had something to do with it, but I think if you research it, cubic dollars had a lot to do with it, as it was costing the manufacturers that were left at the time, which were only a couple besides Honda, millions of dollars each year to compete with bikes that the technology to develop them had nothing to do anymore with what they were manufacturing for the worldwide motorcycle market due to emission requirements worldwide, i.e. 2-stoke versus 4-stoke.

They (sanctioning body/promoter of the series) made the decision to go to a 4-stroke engine, of 1000CC's at first, ran those for several years, then went down to 800CC's for a while, got those motors turning faster lap times than the 1000CC models with development, and now are going back to 1000CC limits as no manufacturer makes an 800CC engine for wide use on the road. It all comes back to being able to write of development costs for the road bikes and let the technology trickle down to them.

This brought Kawasaki, Suzuki, Ducati, and several others back to GP racing as the 2-strokes they were trying to compete with against others, were no longer competitive ( some never were, and some simply chose not to compete in the top class as they did not have product and the cost was prohibitive to develop it) against Honda and Yamaha with the two strokes they were building at the time as they had gone to 4-strokes on the road bikes, were not building 2-stokes anymore (at least in the large road bikes), and they were not willing to continue to spend the large amounts in development costs to compete when there was no payoff for the bikes they were making for sale to the public. I just saw a former GP rider who is now a promoter on a motorsports show last Sunday night talking about just the transmissions that are used at present in the GP bikes costing a MILLION DOLLARS per each.

I would not argue that Honda probably had some input into the formula, but the overiding reason for the demise of the two stoke was emissions and money being spent there was no longer any write off for or benefit in the development on the road bikes, as the road bikes had gone to 4 stokes for that reason (emissions). Plus of course that "Harley " sound versus the Japanese 2-stoke sound of "ring-a-ding-ding".

Would really be interesting to see just what could be done with a two stoke emissions/max power wise if carried to the state of the art as possible today with computerized fuel and spark delivery. It looks as though the outboard manufacturers have just stopped or cut way back on development of 2-stokes in todays economic situation, by going the path of least resistance of 4-stokes, with the exception of the Optimax from Mercury and the 2-stroke product from Bombardier. Even the small engine folks such as the manufacturers of lawn and garden, ATV, Jet Ski and others have felt the heat and given in to the 4-stroke trend. Of course they as mass market manufacturers also have BOD's to answer to and the profit motive to make, unlike the small specialized high performance builder such as GRM and VRP. That is unless the emissions police get really tough and don't want anybody to have any fun anymore.

I have changed the link shown previously in the earlier post referencing the NS500 to a better way to reverence the Honda GP bikes, both 2 and 4 stroke with more info.

ADD: My apologies to Tim Kurcz for hijacking his thread with the last few posts, but since I have always been interested in engine technology, especially two stoke type, when the "oval piston" comment was made I thought it would be interesting to some who may not have been familiar with the engine to give some reference to it.

[Powerabout]

What I meant was they left the smaller GP classes last year so no more GP's with 2 stokes
Clearly they left the 500 class a few years back.
Has any 4 stroke got the the power levels of a 2 stroke yet per cc?
Thanks for the interesting info Bill

[Bill Van Steenwyk]

I heard not too long ago, I believe during the Daytona bike telecast that the Moto GP bikes put out about 200-220 HP out of 800CC. These of course are 4-stroke. I did not hear RPM given but I understand that F-1 car makers including Ferrari had much input on the valve train design of the engines used. The car engines have used pneumatic valve opening and closing for quite some time now and I remember hearing they rev as high as 18,000RPM. I seem to remember hearing that type valve train may have been outlawed recently to help contain cost although I am not positive about that.

The VRP and Rossi 500CC 2-stokes are claiming around 240HP and I have not heard the RPM they develop that at or whether it is dyno proved, although the 125CC single cylinder engines by the same manufacturers were turning 13,500 and supposedly pulling as much as 50HP as long as 8-9 years ago. The 500's of course are 4 cylinders, and each of the larger engine models are simply multiple cylinder models starting at 125CC then 250CC, and going thru 500CC, although the 350CC current models are twin cylinder of the same design as the 250's. (2 cylinder) All have had much more development since then, so I would not doubt that kind of HP with the 500. It may be more than just 1/2 as much HP in the 250CC model as you have less friction loss with only two cylinders instead of four, but the same cylinders, carb size, and expansion chambers. The two cylinder 350CC engines are definitely more "torquey" and have more punch out of a corner than a 4 cylinder of the same displacement or that is what seems to be proven on the race course these days.

[Powerabout]

no demise of 2 stokes check this
http://www.suterracing.com/en/suter500.html

(I think we need a new thread on modern 2 strokes)

[Tim Kurcz]

Good news: On the subject of engine technology - I'm all about it! A thread dedicated to advances in 2 & 4 stroke technology would be great!

Bad news: Regarding the modified Nydahl "laker" exhaust, no deposits were received, so I'm scrapping the project except for my own engines. If I get bored next winter, a few may be built and offered.

For now, it's back to the shop where six customer towers, six exhaust systems, a NBRA 49.9 and 49.9 OMC turbo are in construction.

Enjoy your 2012 season!

Tim

[tunnelboat]

Tim try posting on Screamandfly.com More of a lake racer group..

[Tim Kurcz]

Tim try posting on Screamandfly.com More of a lake racer group..

Thanks Mike,

Will do sometime next winter. Too busy right now anyway. Have a great season!

Tim

[dart]

Bad news: Regarding the modified Nydahl "laker" exhaust, no deposits were received, so I'm scrapping the project except for my own engines. If I get bored next winter, a few may be built and offered.

Enjoy your 2012 season!

Tim
g,day mate,oh thats a shame r.e your exhaust project!!
so with your exhaust project idea,would that allow a two stroke expansion pipe to be succesfully fitted and work and run nicely ??
i really want to fit a jet ski pipe from www.factorypipe.com
you can see my new thread on here r.e expansion pipes,http://www.boatracingfacts.com/forums/showthread.php?14798-Expansion-pipe-on-two-stroke-marine-engine-possble
can you please email me more info/price r.e your exhaust kit??
my email is toprank_mt_racing@hotmail.com
hope to hear from you soon tim
thanks mate
glen

[Fastjeff57]

I recall a photo of Honda's oval piston set up: There were two connecting rods side-by-side, and the length was about 1.5 times the width. This was for a 4 stroke engine, and it had (as I recall) 8 valves, hence the reason for the oval shape.

Jeff

[David_L6]

I recall a photo of Honda's oval piston set up: There were two connecting rods side-by-side, and the length was about 1.5 times the width. This was for a 4 stroke engine, and it had (as I recall) 8 valves, hence the reason for the oval shape.

Jeff

Just Google NR 500 and you'll find photos.

[Tim Kurcz]

g,day mate,oh thats a shame r.e your exhaust project!!
so with your exhaust project idea,would that allow a two stroke expansion pipe to be succesfully fitted and work and run nicely ??
i really want to fit a jet ski pipe from www.factorypipe.com
you can see my new thread on here r.e expansion pipes,http://www.boatracingfacts.com/forums/showthread.php?14798-Expansion-pipe-on-two-stroke-marine-engine-possble
can you please email me more info/price r.e your exhaust kit??
my email is toprank_mt_racing@hotmail.com
hope to hear from you soon tim
thanks mate
glen

Hi Glen,

You can most certainly attach an expansion chamber to the Mod-50 style exhaust system (contact Anthony McCulloch elsewhere on this site). Whether it works or not is another question.

The modified Nydahl system patterened will sell for $495 USD + shipping but will not bolt to your Tohatsu - It's for the OMC 49.9 loop triple only.

To be honest, the Tohatsu triple has a near copy of the OMC Mod-50 pulse tuned exhaust system already. You'll go through alot of effort and expense to improve upon it without significant weight gain.

If you want more than incremental gains, you should consider N2O or a turbo Good luck!

Tim

[calvin]

Which 3 cyl Tohatsu are you referring to?

[dart]

Which 3 cyl Tohatsu are you referring to?
the engine i have and are talking about is the 40/50 hp late model mercury (tohatsu) 3 cylinder/3 carb short shaft japenese spec.
cheers

[Argo]

Are these exhaust systems still available ? Do anyone know if they can be purchased somewhere?

New or used not a big deal for me, if you want to sell your used send me a PM

[Steves Jem]

Good news: On the subject of engine technology - I'm all about it! A thread dedicated to advances in 2 & 4 stroke technology would be great!

Bad news: Regarding the modified Nydahl "laker" exhaust, no deposits were received, so I'm scrapping the project except for my own engines. If I get bored next winter, a few may be built and offered.

For now, it's back to the shop where six customer towers, six exhaust systems, a NBRA 49.9 and 49.9 OMC turbo are in construction.

Enjoy your 2012 season!

Tim
Tim
Are you still considering this project as I would be interested in purchasing 2 of your racing exhausts for the 49.9 ci OMC? I am in Australia so final $ price would need to include shipping. I await your reply.
Regards
Stephen

[Tim Kurcz]

Tim
Are you still considering this project as I would be interested in purchasing 2 of your racing exhausts for the 49.9 ci OMC? I am in Australia so final $ price would need to include shipping. I await your reply.
Regards
Stephen

Hello Stephen,

Thank you for your inquiry. There's a potential customer for the prototype, making a decision Saturday. If his purchase falls through, you can purchase it and make copies in Aussie. Est cost delivered is $625 USD (not including tax/tariff if any). I'll respond with an update next week.

Tim

[Powerabout]

wow, someones going 1250 racing...again?

[Steves Jem]

Hello Stephen,

Thank you for your inquiry. There's a potential customer for the prototype, making a decision Saturday. If his purchase falls through, you can purchase it and make copies in Aussie. Est cost delivered is $625 USD (not including tax/tariff if any). I'll respond with an update next week.

Tim
Tim.
Did your sale eventuate as if it did not I am still interested in purchasing your exhaust system?

Stephen Medaris

[Mumat]

Tim I'm looking forward to seeing the exhaust and parts. By the way long time reader first time poster!

[Tim Kurcz]

Tim I'm looking forward to seeing the exhaust and parts. By the way long time reader first time poster!

Hello Mumat, A check has been sent for the prototype. Once received it's gone, no more will be produced. Apologies, but there's just not enough market to justify the expense for patterns. If you know a good CNC mill guy, just take the photos and he can make them from scratch. Good luck!

Tim

[Steves Jem]

Tim. Sorry to see that your project has not been supported but good to see that some has purchased you patterns. I have down loaded your pictures and will commence trying to duplicate your design. There maybe quite a few in Aus interested but it will take some time to produce.


Stephen

[Mumat]

I received my exhaust from Tim. I i got my block back from my machinest and finaly got all my parts and some free time. I have it put tog geater as a long block 58653 as soon as I get it running I'll post up more picks

[Mumat]

59780
Just a quick update its ready to fire. I'm working on the hood and some paint not my strong suite but I get buy. I'm better at building than painting.

[Mumat]

update I have fired up the motor and its braking in It has a great deep exhaust note one you would not expect from a 75 hp jhonson. Tim Kurcz ported the block for me and gave some great advice thanks Tim!

[Tim Kurcz]

update I have fired up the motor and its braking in It has a great deep exhaust note one you would not expect from a 75 hp jhonson. Tim Kurcz ported the block for me and gave some great advice thanks Tim!

Hi Brad,

How about posting some images?

Tim

[ice_spy]

Good read, and great work. I use to play with jetskis and the power pipe was always one of the best power improvements you could do to the 2 stroke. I have been thinking if it's possible to squeeze in an expansion chamber power pipe down the leg. I'm guessing not as the pulses would not be able to be tuned due to the lack of circumference inside the leg. If it could be done cooling could be changed to feed water into the pipe. The tohatsu M50D exhaust tube actually has an opposite type of pipe with the narrow section in the middle and cones out at both ends. Different diameters and lenghts have not seen a gain over this factory M50 D1 design and is sort after for people running the D2 due to availabilit, the D1 no longer in production. The sound would be nice too.

[Tim Kurcz]

Tim
Are you still considering this project as I would be interested in purchasing 2 of your racing exhausts for the 49.9 ci OMC? I am in Australia so final $ price would need to include shipping. I await your reply.
Regards
Stephen

Hi Stephen,

Are you talking about my top-outlet open meg system? If so, each system is $595 USD shipping would be about $150, so you're in for about $1350 USD. This includes the exhaust system, fasteners, and gasket ready for assembly.

Tim

[Steves Jem]

Hi Stephen,

Are you talking about my top-outlet open meg system? If so, each system is $595 USD shipping would be about $150, so you're in for about $1350 USD. This includes the exhaust system, fasteners, and gasket ready for assembly.

Tim

Tim

No it is not the top-outlet open meg system as these would be too noisy for Australia. The exhaust system that would have suited was the one that you sold to Mumat but I will keep the open one you have in mind.

Stephen

[Tim Kurcz]

Tim

No it is not the top-outlet open meg system as these would be too noisy for Australia. The exhaust system that would have suited was the one that you sold to Mumat but I will keep the open one you have in mind.

Stephen

Sorry Stephen,

The system that Mumat has is a one off prototype, and my only pattern. There weren't enough Lakers willing to invest in the tooling, so I discontinued the project.

As it turns out, the belly pan and upper cowl both needed modification to fit the exhaust system - more work than most people want to do, or are capable of. In this case the proto went to the right guy. Hopefully he will post some pics.

Tim

[sharpeye Mike]

I gather it would of fit perfectly under an SST60 pan and cowl.

[Tim Kurcz]

I gather it would of fit perfectly under an SST60 pan and cowl.

Possibly, but unknown. It was more like a Mercury T2-X protruding thru the narrow cowl.

Tim

[Mumat]

http://s1062.photobucket.com/user/slowmo11/media/Mobile%20Uploads/2015-07/B17639A2-2C22-4522-AB17-1B6B9ECFD399_zpskt8p4hfc.mp4.html?o=173

This is a short vid of the first fire it was a rigg to get it running I since have cleaned it up and got it looking a lot cleaner

[Steves Jem]

http://s1062.photobucket.com/user/slowmo11/media/Mobile%20Uploads/2015-07/B17639A2-2C22-4522-AB17-1B6B9ECFD399_zpskt8p4hfc.mp4.html?o=173

This is a short vid of the first fire it was a rigg to get it running I since have cleaned it up and got it looking a lot cleaner

Sounds great but can you do a video on the exhaust side.

Stephen

[Mumat]

I'll look I may have some pictures and or Video hiding a round the motor is in storage till you get my garage construction done.

[Mumat]

http://s1062.photobucket.com/user/slowmo11/media/Mobile%20Uploads/2015-07/11759370-742D-4F3D-BBDC-FAE8CB8677BA_zpsdh2kdokm.mp4.html
Try this link I got lucky

[Jippe]

What size that chamber needs to be? Is there some formula to calculate it?

[Tim Kurcz]

What size that chamber needs to be? Is there some formula to calculate it?

Experimentation suggests that 150% of the exhaust port area with a 25% choke immediately downstream of the #3 cylinder followed by a 3 degree divergence cone is a good starting point.
Best of luck!

[Steves Jem]

Tim
Started on an exhaust system for the stock 49ci 3 cylinder OMC Stinger based upon the Mod 50 exhaust. Found the information you posted and others very helpful. Parts have been casted and are awaiting machining. It will be some time until it will be tested. Will try to post some pictures when completed. There are quite a few guys here in AU who are interested.

[Mumat]

I have been insanely busy but my 75 is togeather I had to Modify the pan and hood for my exhaust but it turned out looking good. I'll get more picks when the snow clears.

[filthy phill]

Need to get it on the water and see what she goes like,
looks very nice all painted up.

[Steves Jem]

I have been insanely busy but my 75 is togeather I had to Modify the pan and hood for my exhaust but it turned out looking good. I'll get more picks when the snow clears.

Any updates on how this exhaust performs? Would love to know the difference in performance.

Stephen